Since unused tags are automatically deleted in 24-36 hours so I guess this should not be of any concern. However, some users may try to use this for rep harvesting. Create new tags, edit tag-wiki, and earn 2 points. Usually improper tags are promptly removed from posts by users with edit privileges. So that tag becomes eligible for automatic removal. What I dont know is whether the system deducts 2 points (of tag wiki edit) when that tag is deleted. This rep deduction happens for normal post editing, if the post that you had edited earlier is deleted you do loose 2 points which you gained earlier.
Btw, number of questions posted under that tag is not displayed anywhere on the suggested edit review page. So slight benefit of the doubt can be given to the approvers.